Excavating tool tooth

ABSTRACT

An excavating tool tooth includes a mounting area (10) and a working area (11). The working area (11) includes longitudinal bars (14-18) made of a hard material. The bars are inserted in the steel and snugly contact the tooth&#39;s cutting face. The presence of the rods made of a hard material substantially increases the tooth&#39;s service life. The bars are produced by infiltration.

BACKGROUND OF THE INVENTION

The present invention relates to excavating tools such as revolvingcutter head excavators for use in mines or dredgers.

Revolving cutter head excavators consist of a drive wheel that rotatesaround a shaft and is driven by a means of rotation. The periphery ofthe revolving cutter head excavator has a series of buckets equippedwith teeth arranged in directions that are essentially radial. Dredgersdo not have buckets and their teeth are distributed around the peripheryin a rotary ogival structure. Each tooth consists of a single-unit toothbody structure made of a mechanically resistant metal or alloy such assteel, having a fixing area to connect it to the bucket or the ogivalstructure and a working area to dig the soil. The working area isgenerally flat and shaped like a shovel and is bounded by a leading facethat points in the direction of movement of the periphery of the wheelor ogival structure in the preferred direction of rotation and atrailing face or face opposite the leading face. The leading face andthe trailing face are generally flat or slightly curved and areconnected by a front tapered facet that defines a transverse cuttingedge. If the tooth is mounted on the bucket or the ogival structure, thetransverse cutting edge is essentially parallel to the axis of rotationof the assembly and the general plane formed by the tooth shovel orworking area generally slants in the direction of the direction ofmovement of the tooth in the preferred direction of rotation.

During operation, part of the peripheral zone of the bucket or cuttercuts into the ground, the transverse cutting edge of the teeth bitesinto the ground and the leading face pushes up the material. Thisresults in considerable wear of the transverse cutting edge and theleading face.

One common solution to increase the service life and the efficiency ofthe teeth is to hardface the external surface of the leading face andthe tapered front facet in order to cover them with a coat of moltencarbide by fusing a welding bead.

Although this process significantly increases the service life of thetooth, wear still occurs, relatively slowly at the start of use when thehard material still covers the front facet; wear then becomes muchfaster when the hard material that covers the front facet is itselfdamaged by wear. The tooth can only be used as long as the length of itsworking area has not reduced too extensively and this defines themaximum permissible area of wear of the tooth.

In particular, as soon as the front facet has lost its protectivecoating of hard material, wear becomes much faster despite the existenceof a layer of hard material on the leading face of the tooth.

Another drawback of known structures is that they require the use of aprotective surface hardfacing, a layer that is produced by melting witha welding torch or an electric arc. An examples of such a layercomprises a deposit consisting of a mixture of molten carbide particlesembedded in a fusible matrix. Such hardfacing is time consuming andawkward and produces relatively irregular surfaces made up by thejuxtaposition of several side-by-side welding beads. The intermediateareas between two successive beads are usually sunken areas of which themetallurgical structure is slightly different from the central structureof the welding beads. This results in a lack of homogeneity of thematerial that forms the protective layer made of a hard material andthis results in the appearance of preferential areas of wear, thusencouraging faster wear of the material. In addition, such a process isexpensive and requires skilled labor.

Dredger teeth with a composite structure are known consisting of a metaltooth body containing inserts of a hard anti-abrasion material. Indocument U.S. Pat. No. 3,805,423, a prefabricated insert is fitted inappropriate recesses in the metal tooth body where it is fixed bywelding or brazing. The insert, in the embodiment shown in FIGS. 3 and4, consists of two intermediate bars which each take up half the heightof the tooth. Document U.S. Pat. No. 4,052,802 also describes providinga prefabricated insert and fitting it in the tooth body. The insert issandwiched between the metal surface plates, between which it isassembled by brazing. Therefore the insert does not take up the entireheight of the tooth. There is no suggestion in this document ofreplacing the metal plates by a material containing particles of a hardmaterial.

In document FR-A-2 373 500, an excavating tool is produced by providingcover plates made of sintered carbide on a steel body. The steel body iscast around the cover plates.

There is no suggestion in this document of replacing the internal steelbody by a material containing particles of hard material. In any case,this results in an extremely fragile tooth.

The structures and production processes described in documents U.S. Pat.No. 4,052,802 and FR-A-2 373 500 are not compatible with each other. Infact, producing a tooth with an internal insert made of particles ofhard material in accordance with document U.S. Pat. No. 4,052,802 isachieved by assembling several subassemblies by brazing whereas documentFR-A-2 373 500 makes provision for such assembly by molding from acasting. The expert is therefore not encouraged to cosine the teachingsof instruction in these two documents.

In document U.S. Pat. No. 3,286,379, fingers of hard material areproduced by casting a hard material in longitudinal grooves in the metaltooth body. Document JP-A-62 99 527 describes a tooth for an excavatingtool in which the prefabricated inserts are formed from sintered carbideand are assembled on the tooth body by brazing.

It seems that these known structures with longitudinal inserts do notgive the expected results in terms of efficiency and long service life.In fact, fairly rapid wear is observed on the tooth, particularly due toflaking of the bars made of hard material. The bars of hard materialwhich do not take up the entire height of the tooth do not provide asufficient increase in the service life of the tooth and theirmanufacturing process does not allow sufficient cohesion of thecomponents of such a heterogenous structure.

One of the main objects of the present invention is to avoid thedisadvantages of known excavating tool teeth structures and theirproduction processes; it initially proposes a new composite toothstructure consisting of several longitudinal bars of hard material thattake up the entire height of the tooth. The new tooth structure iscompatible with the presence of protective surface layers made of amolten hard material but can also be used without such a protectivesurface layer.

One of the problems is that, with usual brazing or welding processes, itis awkward or difficult to correctly insert and join bars that take upthe entire height of the tooth without adversely affecting themechanical properties of the anti-abrasion material that constitutes thebars. The invention solves this difficulty by using a new infiltrationprocess on the tooth blank itself.

The invention suggests producing such a tooth structure by means of aso-called infiltration process. The infiltration process can beimplemented in a relatively simple manner and does not require greatskill on the part of the user, unlike hardfacing techniques using awelding bead, and also results in lower production costs. The processavoids the tricky operation of having to solder or braze an insert.

When such an infiltration process is used, the tooth structure thusobtained is characterized by the fact that the bars of hard material arebonded to the metal of the tooth body by a brazing alloy that forms thematrix which itself links the particles of hard material to each other.This feature seems particularly important in order to obtainsatisfactory cohesion between the bars of hard material and the metalthat forms the tooth body.

When using such an infiltration process, the mold structures areparticularly small and easy to produce because the metal parts of thetooth structure themselves act as a mold.

The invention makes it possible to considerably improve the service lifeand efficiency of an excavating tool tooth to a surprising extentcompared with familiar techniques given comparable quantities of hardmaterial. The tooth continues to cut as it wears.

Finally, the risk of breakage or flaking of the coating and the bars ofhard material is significantly reduced; this risk is often encounteredwith known teeth.

The invention therefore makes it possible to obtain better cohesion ofthe excavating tooth, improved hardness of the bars of hard material andgreater ease of production.

SUMMARY OF THE INVENTION

In order to achieve these objects as well as others, the tooth for anexcavating tool in accordance with the invention has a general structurethat is similar to known teeth; however, the working area of the toothaccording to the invention has bars consisting of a mixture based onparticles of hard material bonded in a matrix, the said bars beingembedded in the metal of the tooth body and forming longitudinal barsthat are essentially perpendicular to the transverse cutting edge. Thelongitudinal bars made of hard material form a row of bars that areinserted into the interstices of a metal comb constituted by the rest ofthe structure of the body. In those parts of the cross section thatcontain longitudinal bars with particles of hard material, the materialwith particles of hard material ideally takes up the entire height ofthe tooth between the leading face and the trailing face.

In one possible embodiment, the longitudinal bars of hard material areseparated from the front facet by a metal area or metal crosspiece. Thisstructure makes it easy to produce the tooth by infiltration because themetal crosspiece then forms part of the mould to contain the moltenmaterial intended to form the bars.

In one particular embodiment, the longitudinal bars made of hardmaterial are linked to each other by bridges of hard material of whichthe height is less than that of the bars and with which they form aplate of hard material that constitutes the central part of the leadingface. In this case, the front ends of the bars made of hard material canusefully be joined to each other by a crosspiece made of a hard materialof which the height is essentially equal to the height of the bars.

Further objects, characteristics and advantages of the present inventionwill be apparent from the following description of particularembodiments, reference being made to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagrammatic cross section of a dredger;

FIG. 2 is a top view of a tooth showing the leading face;

FIG. 3 is a side view of the tooth in FIG. 2;

FIG. 4 is a bottom view of the tooth in FIG. 2 showing the trailingface;

FIGS. 5 to 7 show the leading face, a profile view and the trailing faceof a tooth respectively in another embodiment of the invention;

FIG. 8 is a longitudinal cross section along plane A--A in FIG. 9;

FIG. 9 is a top view of the tooth in FIG. 5, a longitudinal crosssection along plane B--B in FIG. 8;

FIG. 10 is a cross section along plane C--C in FIG. 9;

FIGS. 11, 12 and 13 are views similar to FIGS. 8, 9 and 10 respectivelyin a second embodiment of the invention;

FIGS. 14, 15 and 16 are views similar to FIGS. 8, 9 and 10 in a thirdembodiment of the invention;

FIGS. 17, 18 and 19 are views similar to FIGS. 8, 9 and 10 respectivelyin a third embodiment of the invention;

FIGS. 21 and 22 are views similar to FIGS. 9 and 10 respectively in afourth embodiment of the invention with FIG. 20 being a longitudinalcross section along plane D--D in FIG. 21; and

FIGS. 23 to 27 illustrate the stages in a process to produce teeth inaccordance with the invention by infiltration.

DETAILED DESCRIPTION OF THE INVENTION

In the embodiment diagrammatically shown in FIG. 1, an excavating toolsuch as a dredger or a revolving cutter head excavator for use in a minegenerally consists of a rotating carrier structure 1 mounted so that itrotates on a drive shaft 2 and is driven by means of rotation around apreferred axis of rotation represented by arrow 3. The periphery 4 ofthe rotating carrier structure is fitted with teeth such as tooth 5pointing in generally radial directions facing slightly in the directionof preferred direction of rotation 3 as shown in the Figure. The teethare all normally identical. Tooth 5 consists of a leading face 6pointing towards the preferred direction of rotation 3, an oppositetrailing face 7 and a front facet 8 that defines a transverse cuttingedge 9. Transverse cutting edge 9 is essentially parallel to the axis ofrotation 2 of the wheel.

Tooth 5 is shown in greater detail in FIGS. 2 to 4. FIGS. 2 to 4 onlyshow the outer surface of the tooth which can be a traditional tooth ora tooth in accordance with the present invention.

As shown in FIGS. 2 to 4, a tooth of an excavating tool in accordancewith the invention consists of a tooth body structure made of amechanically resistant metal or alloy such as steel having a fixing area10 to join it to the drive wheel structure and a working area 11 to digthe soil. Fixing area 10 can be of the traditional type and has nospecial effect as far as the present invention is concerned. Theinvention deals with working area 11.

Working area 11 is generally flat, shaped like a shovel and limited byleading face 6, trailing face 7, front facet 8 and two lateral edges 12and 13. Leading face 6 and trailing face 7 are generally flat, slightlycurved and, if applicable, parallel to each other. Front facet 8 istapered. The tooth therefore has a transverse cutting edge 9.

Traditional teeth generally have coating layers made of a hard materialsuch as layers based on particles of molten tungsten carbide embedded ina metal matrix. Leading face 6, front facet 8 and lateral edges 12 and13 are covered in a protective layer of hard material.

The structure according to the invention is characterised in particularby the presence and the shape of the areas of hard material embedded inthe metal structure of working area 11. Such areas of hard material areapparent, for example, in the embodiment on FIGS. 5 to 7: FIG. 5 shows,on leading face 6, five rectangular areas 14, 15, 16, 17 and 18respectively. The hard material consisting of a mixture based onparticles of hard material bonded in a matrix just shows on the surfaceof leading face 6 in the five rectangular areas which are regularlyspaced relative to each other and have longitudinal axes. Therectangular areas are close to transverse cutting edge 9 butnevertheless do not touch the cutting edge. Likewise, similarrectangular areas 19, 20, 21, 22 and 23 on trailing face 7 are shown inFIG. 7. In reality, the respective areas such as area 17 in FIG. 5 andarea 22 in FIG. 7 are the exposed faces of a bar 24 (FIG. 8) consistingof a hard material inserted in a slot that crosses the metal forming thebase structure of working area 11.

FIGS. 8 to 10 show various cross sections and longitudinal sections ofthe tooth in FIGS. 5 to 7. FIG. 8 is a longitudinal section along aplane that is perpendicular to leading face 6 and bisects the bar madeof hard material 24 in FIG. 9 corresponding to surfaces 17 in FIG. 5 and22 in FIG. 7. The hard material of bar 24 is laterally limited by twointermediate metal spars 25 and 26, by the base 27 of the working areametal structure and by an end metal crosspiece 28. The material of bar24 is apparent on leading face 6 to form rectangular area 17 and isapparent on trailing face 7 to form rectangular area 22.

In this embodiment, the working area metal part 11 has a series oflongitudinal slots separated by spars, for example six spars 25, 26, 29,30, 31 and 32 which define five slots to accommodate five bars 24, 33,34, 35 and 36. The longitudinal slots are filled with anti-abrasion hardmaterial such as tungsten carbide or the like. The metal spars are alllinked on the one hand to the base of metal structure 27 and, on theother hand, to front metal crosspiece 28.

In this embodiment, the outer faces of the tooth are not covered in aprotective anti-wear layer based on a hard material. The presence ofinternal areas of hard material such as bar 24 is sufficient to delaywear of the tooth considerably.

The structure shown in FIGS. 11 to 13 is similar to that in FIGS. 8 to10: the internal structure is identical; the only difference is thepresence of an external protective layer 100 of hard material such asparticles of molten tungsten carbide bonded by a metal matrix, theexternal surface of the said protective layer forming the leading face6, the front facet 8 and the lateral edges 12 and 13. The externalappearance of such a tooth is identical to that shown in FIGS. 2 to 4.

The embodiment shown in FIGS. 14 to 16 is similar to that in FIGS. 11 to13 and only differs from it in that metal crosspiece 28 has beenomitted. In this case, the metal spars such as spars 25 and 26 havefront ends that are free and are not joined and space 24 is an openslot. The metal spars therefore form a kind of comb of which theinterstices are occupied by a row of bars made of hard material. Thehard material that fills the interstices such as space 24 extends as faras protective layer 100 of which the external surface forms frontcutting facet 8. As an alternative, one can use the same internal toothstructure without external protective layer 100.

In the embodiment in FIGS. 17 to 19, the structure is similar to that inthe embodiment in FIGS. 14 to 16. It differs from it in that, in thefront area of lateral edges 12 and 13, the thickness of protective layer100 made of hard material is increased. These areas are actuallypreferred areas of wear that are subjected to wear stresses that exceedthose to which the other working parts of the tooth are subjected. Ithas been observed that a slight increase in the thickness of theprotective layer in both these lateral parts results in a significantincrease in the service life of the tooth.

The embodiment shogun in FIGS. 20 to 22 differs from the aboveembodiments in that bridges of hard material are provided in order tolink the successive internal bars made of hard material of the tooth. Asin the embodiment in FIGS. 8 to 10, the metal structure of the toothconsists of a metal base 27 to which intermediate spars 25, 26, 29 and30 are connected as well as two lateral spars 31 and 32. The front endsof lateral spars 31 and 32 are linked by metal crosspiece 28.Intermediate metal spars 25, 26, 29 and 30 have free front ends that areoffset from metal crosspiece 28. The hard material thus formslongitudinal bars 24, 33, 34, 35 and 36 and the front ends of the barsare linked to each other by a crosspiece 37 made of hard material.Crosspiece 37 made of hard material can ideally take up the entireheight of the working part of the tooth, i.e. the entire distanceseparating leading face 6 and trailing face 7 as shown in FIG. 20. Inthis case, during use, metal crosspiece 28 wears out fairly quickly andexposes crosspiece 37 made of hard material which counteracts wear.Similarly, metal lateral spars 31 and 32 wear out fairly quickly andthen expose lateral bars 33 and 36 made of hard material whichcounteract wear.

In this same embodiment, longitudinal bars made of hard material arelinked to each other by bridges of hard material of which the height isless than that of the bars and with which they form a plate of hardmaterial that constitutes the central part of leading face 6. As shownin FIG. 22 in a cross section, longitudinal bars 24 and 33 made of hardmaterial are linked by bridge 38. FIG. 20 is a longitudinal sectionalong plane D--D in FIG. 21 and shows a longitudinal section of thissame bridge 38. Bridges 39, 40 and 41 link the other longitudinal barsmade of hard material two by two. In other words, the height oil theintermediate metal spars is less than the total height of the workingpart of the tooth so that the hard material covers intermediatelongitudinal bars on the leading face 6 of the tooth.

In all the embodiments described above, the bars made of hard materialcan be approximately 4 to 15 mm thick and can be separated by metalareas or metal spars that are roughly 4 to 15 mm thick. The thickness isdefined as the dimension in a direction parallel to transverse cuttingedge 9. The length of the bars of hard material is essentially equal tothe length of the maximum permissible area of wear of the tooth. Thehard material that forms the longitudinal bars can ideally containparticles of molten tungsten carbide, preferably spheroidal particleswith no sharp-angle areas. Improved anti-wear characteristics areobtained by using a mixture of particles of different sizes, someparticles of molten tungsten carbide having a diameter equal to orgreater than 2 mm.

In accordance with the invention, the preferred process shown in FIGS.23 to 27 to produce internal areas of hard material such as thelongitudinal bars, comprises the following steps:

a) According to FIG. 23, produce a blank 42 made of metal or alloyhaving a fixing area 10 and a working area metal part 11, the saidworking area metal part consisting of a series of longitudinal slots 43that terminate at least on leading face 6 and are separated by spars 25,26, 29, 30, 31, 32;

b) According to FIG. 24, place the said blank 42 on a mounting 44 withits leading face 6 upwards and in an essentially horizontal direction;

c) According to FIG. 25, fill the said longitudinal slots 43 withparticles of a hard anti-abrasion material 45 such as molten tungstencarbide or the like and vibrate this assembly so that the particles arein as close as possible contact with the walls of the slots and arecontiguous to each other;

d) According to FIG. 25, prepare a sufficient quantity of an appropriatealloy 46 in a form suitable to ensure subsequent distribution of thealloy during a subsequent melting phase, the alloy being a brazing alloycapable of wetting the particles of hard material 45 and the materialwhich forms blank 42 and of melting at a temperature less than themelting temperature of blank 42 and mounting 44;

e) According to FIG. 26, heat this assembly to a temperature higher thanthe melting point of alloy 46 and lower than the melting point of blank42 and mounting 44 in order to ensure infiltration of the molten alloybetween the particles of hard material 45;

f) According to FIG. 27, allow to cool and separate the piece thusobtained from its mounting.

In the embodiment described with reference to FIGS. 23 to 27, blank 42is such that intermediate metal spars 25, 26, 29 and 30 are offset fromleading face 6 which is defined by outer spars 31 and 32. In this way,during the filling and infiltration stage in FIG. 25, hard material 45fills slots 43 and covers intermediate spars 25, 26, 29 and 30 in orderto produce a plate of infiltrated hard material 47 which is shown inFIG. 27 and forms the central area of leading face 6.

According to one variation, front ends of outer spars 31 and 32 arelinked to each other by a metal crosspiece such as crosspiece 28 shownin FIG. 20 whereas intermediate spars 25, 26, 29 and 30 have a free endwhich is separated from crosspiece 28 by a gap. In this way, during thefilling and infiltration stage illustrated in FIG. 25, hard material 45fills the said gap which separates the free ends of the intermediatespars and metal crosspiece 28 in order to form a crosspiece 37 of hardmaterial such as that shown in FIGS. 20 and 21.

This process is compatible with a subsequent stage during which one canproduce a surface coating 100 of hard material on leading face 6 andfront facet 8 as shown in FIGS. 11 to 16. Surface coating 100 of hardmaterial can, for instance, be produced by fusing a welding bead with awelding torch or electric arc using conventional hardfacing processes bywelding.

In order to improve the cohesion between the tooth body metal structureand the parts made of hard material, one can carry out, beforeinfiltration and welding, an initial operation to prepare the surface ofthe blank which is in contact with the hard material. Such preparationmay include the following phases:

Grinding or shot blasting of the surface,

Plating of a thin film of alloy of the self-fusingnickel-chrome-boron-silicon type by means of a welding torch.

The present invention is not confined to the embodiments explicitlydescribed and it includes the various variations and generalizationscontained in the scope of the invention as defined in the appendedclaims. In particular, one can, without exceeding the scope of theinvention, provide a number of bars of hard material other than five,bars having cross sections other than a rectangular cross section andshapes of the leading and trailing tooth face which are not flat.

I claim:
 1. Tooth for excavating tool comprising a tooth body structuremade of a mechanically resistant metal or alloy having a fixing area(10) to join said tooth to a drive structure (1) and a working area (11)to dig the soil, the working area (11) being limited by a leading face(6) and a trailing face (7) which are connected by a front tapered facet(8) that defines a transverse cutting edge (9), the working area (11)having a row of bars (24, 33, 34, 35, 36) made of a mixture based onparticles of hard material bonded in a matrix, said bars beinglongitudinal and essentially perpendicular to said transverse cuttingedge (9) and forming a row of bars inserted in the interstices of ametal comb with several metal or alloy spars (25, 26, 29, 30, 31, 32)made up by a remainder of the body structure,characterized in that, inthose parts of the cross section that include longitudinal bars made ofparticles of hard material (24, 33, 34, 35, 36), the bars with particlesof hard material take up an entire height of the tooth between theleading face (6) and the trailing face (7).
 2. Tooth according to claim1, characterized in that the longitudinal bars made of a mixture used onparticles of hard material (24, 33, 34, 35, 36) are separated from thefront facet (8) by a metal crosspiece (28).
 3. Tooth according to claim2, characterized in that the longitudinal bars made of a mixture basedon particles of hard material (24, 33, 34, 35, 36) are linked to eachother by bridges of hard material (38, 39, 40, 41), the bridges having aheight, the height of the bridges is less than that of the bars, whereinsaid longitudinal bars form a plate of hard material (47) whichconstitutes the central part of the leading face (6).
 4. Tooth accordingto claim 3, characterized in that the front ends of the bars of hardmaterial (24, 33, 34, 35, 36) are joined to each other by a crosspiecemade of hard material (37) the height of which essentially equals theheight of the bars.
 5. Tooth according to claim 1, characterized in thatthe bars made of a mixture based on particles of hard material (24, 33,34, 35, 36) are roughly 4 to 15 mm thick and are separated by metal oralloy spars (25, 26, 29, 30) which are roughly 4 to 15 mm thick. 6.Tooth according to claim 1, characterized in that the bars made of amixture based on particles of hard material (24, 33, 34, 35, 36) areessentially as long as a length of the maximum permissible area of wearof the tooth.
 7. Tooth according to claim 1, characterized in that theleading face (6) and front facet (8) of said working area and lateraledges (12, 13) of said tooth are covered in a layer (100) of materialbased on particles of hard material bonded in a matrix.
 8. Toothaccording to claim 1, characterized in that the longitudinal bars madeof a mixture based on particles of hard material (24, 33, 34, 35, 36)contain particles of molten tungsten carbide.
 9. Tooth according toclaim 8, characterized in that some of the particles of molten tungstencarbide have a diameter equal to or greater than 2 mm.
 10. Toothaccording to claim 1, characterized in that the bars made of a mixturebased on particles of hard material (24, 33, 34, 35, 36) are bonded tothe metal of the tooth body structure by a brazing alloy forming thematrix that links the particles of hard material.
 11. Process to producea tooth for an excavating tool of the type consisting of a tooth bodystructure made of metal or alloy which is mechanically resistant havinga fixing area (10) to join it to a drive structure (1) and a workingarea (11) to dig the soil, the working area being limited by a leadingface (6) and a trailing face (7) which are connected by a tapered frontfacet (8) defining a transverse cutting edge (9), the working areahaving bars (24, 33, 34, 35, 36) made of a mixture based on particles ofhard material bonded in a matrix, said bars being embedded in the metalof the tooth body and forming longitudinal bars that are essentiallyperpendicular to said transverse cutting edge (9), said process beingcharacterized in that it comprises the following steps:a) producing ablank (42) made of metal or alloy having the fixing area (10) and theworking area (11), said working area having a series of longitudinalslots (43) opening out into said leading face (6) and said trailing face(7) and separated by spars (25, 26, 29, 30, 31, 32); b) placing theblank (42) on a mounting (44) with its leading face (6) upwards so thatsaid blank is essentially horizontal; c) filling said longitudinal slots(43) with particles of a hard anti-abrasion material (45) such as moltentungsten carbide vibrating the blank and the mounting so that theparticles are in as close as possible contact with the walls of theslots and are contiguous with each other; d) preparing a sufficientquantity of a brazing alloy (46) which has a melting temperature lessthan the melting point of the blank (42) and the mounting (44); e)heating the blank, the mounting and the brazing alloy to a temperaturehigher than the melting temperature of the brazing alloy (46) and lowerthan the melting point of the blank (42) and the mounting (44) in orderto create a molten brazing alloy and to ensure the infiltrating of themolten brazing alloy between the particles of hard material to wet theparticles of hard material and the metal or alloy which forms the blankand the mounting; and f) allowing the blank and the mounting to cool andseparating a finished piece from the mounting.
 12. Process according toclaim 1, characterized in that the process includes an initial operationto prepare the surface of the blank which is in contact with the hardmaterial, the initial operation consisting of the followingphases:grinding the surface, plating the surface with a thin film ofalloy of the self-fusing nickel-chrome-boron-silicon type by means of awelding torch.
 13. Process according to claim 11, characterized inthat:the blank (42) is such that the intermediate metal spars (25, 26,29, 30) are offset from leading face (6) defined by the outer spars (31,32), during the filling and infiltration stage, the hard material (45)fills the slots (43) and covers the intermediate spars to make a plateof infiltrated hard material (47) forming the central area of leadingface (6).
 14. Process according to claim 13, characterized in that:thefront ends of the outer spars (31, 32) are linked to each other by ametal crosspiece (28) whereas the intermediate spars (25, 26, 29, 30)have a free end that is separated from the metal crosspiece (28) by agap, during the filling and infiltration phase, the hard material (45)fills the said gap separating the free ends of the intermediate sparsand the metal crosspiece (28) to form a crosspiece of hard material(37).
 15. Process according to claim 11, characterized in that theprocess includes a subsequent stage to produce a surface coating (100)of hard material that covers, in particular, the leading face (6) andthe front facet (8).
 16. Process according to claim 11, characterized inthat the process includes an initial operation to prepare the surface ofthe blank which is in contact with the hard material, this preparationstage consisting of the following phases:shot blasting the surface,plating the surface with a thin film of alloy of the self-fusingnickel-chrome-boron-silicon type by means of a welding torch.